Thermostat.



H. E. REEVE.

THERMOSTAT.

APPLICATION FILED JULY 26,1912;

2 QfiGO, Patented Jan. 16, 1917.

WITNESSES ,1 fl I UNITED STATES PATEN OFFICE.

HENRY E. nEEvE, or NEW YORK, NI Y.

.T'HERMOSTAT.

Specification of Letters Patent.

Patented Jan. 16, 1917.

Application filed July 26, 1912. Serial No.71 1,749.

To all whom it may concern:

Be it known that I, HENRY E. REEVE, a citizen of the United States, and resident of New York, in the county of Kings and State of New York, have invented certain new and useful Improvements in Thermostats, of which the following is a specification.

My invention relates particularly to thermostatic devices for electric alarm circuits.

It has been customary in some devices of this character to employ thermostatic ele-' ments in the form of a bi-metallic arm or coil as it is sometimes called, one end of the coil being fixed and the other end free to move. Adjacent the movable end usually is stationed an adjustable contact. Upon increase in temperature the circuit is closed by the movable end of the coil engaging the stationary contact. These coils being of considerable length are subject tovibrations and are some times distorted accidentally or intentionally so as to alter the temperature at which the circuit is closed.

The main object is to provide a simple and efiicient' device which is reliable under all conditions. Among the specific objects of my invention are the following; to provide. a construction in which the electric yoke having a minimum capacity for ther mal conductivity so as to minimize loss of heat or sudden rise of temperature. Each arm is preferably supported by a U-shaped member and one or both of these may be adjusted. The adjustment is so effected that there is no danger of its being altered accidentally. The end of each arm may be protected b a guard to prevent injury by a me- 7 6 chanica shock. Each arm may be provided with a plurality of small openings extending throughout its entire length so'as to afford a maximum exposed area. 8 Each arm may be also slitted longitudinally along its cen ter line so as to prevent buckling due to transverse expansion and contraction. Each arm may also be slightly tapered in thickness from its base'to its tip, the thickness at the base being say twenty-thousandths and at the tip fifteen-thousandths of an inch. It will be obvious that the device may be made to embody all of these features of construction or that certainadvantages may be had in using one or more features as herein set forth.

Figure 1 shows the construction and arrangements of the parts of a thermostat embodying the preferred form of my invention. Fig. 2, is a detail perspective view showing the'means for effecting the adjustmentof one of the arms. Fig. 3, is a perspective view showing the anchorage device for one of the arms. Fig. 4, is a perspective view of one of the arms and showing the guard device for its tip. -Fig. 5, is a view similar to Fig. 1 showm certain modifica: tions of construction. Fig. 6, shows a'v pair of thermostatic arms with dotted lines indicating the direction of movement of the contact tips. Fig. 7, is a perspective view of a contact arm.

The "arms 1 and 2 are electrically connected to the circuit terminal plates 3 and 4:. The shape, size and method of supporting and insulating the circuit terminal plates is immaterial to thisinvention. The arms 1 and 2 are formed of composite sheets consisting for instance of layers of steel and brass and in the arrangement shown the left hand arm 1 has its outer face of brass and its inner face of steel while the right hand arm has its inner face of brass and its outer face of steel.

For convenience in manufacture, assembling and adjustment each terminal plate may have integral with'it a 'U-shaped support such as 5 bent rip-out of the planeof the main body of the terminal plate, one side of the U-shaped member being integrally united with the terminal plate and the other side of the U-shaped member serving as a support for the'thermostatic arm. A yoke having lugs such as 7 riveted-or other-, "wise suitably secured to the support 5 serves as an anchorage device for the thermostatic arm, the upper and lower portions of the yoke being slotted as at 8 to receive the end of the thermostatic arm. The end of the arm may have a projection such as and the slot may be provided with a similar shaped ofi-set portion to receive the said projection whereby to prevent longitudinal disengagement of the thermostatic arm from its support.

In the anchorage device the corners of the thermostatic arm may be bent over as at; 13 as indicated to prevent the arm from being movable edgewise from the slot 8. While this method of anchorage insures a good electrical circuit, it reduces to a minimum the metallic mass and-thus reduces the loss of heat. This form of connection also makes a clean cut anchorage confined to one cross. section instead of being distributed over a considerable portion of the length of the arm as when riveted and soldered as has been customary. This also avoids the use of solder and the treacherous solder fillets sometimes present.

The thermostatic arm may be readily adjusted by means of a screw such as 10 passing through the movable side of the U-shaped support 5 and screwing into the fixed portion. The screw may be prevented from working loose by providing teeth or projections such as 11 underneath the head of the screw and notches such as 12 in the support. The yielding nature of the U-shaped support will enable the screw to be turned by force even when the projections ll areseatedin the notches 12 but will prevent accidental turning or working loose of the screw.

The freely movable end of the thermostatic arm is guarded by a slotted plate such as 14 which is shown in Figs. 1 and d as suitably secured to the terminal plate. This guard prevents the bending of the arm by mechanical shock and thus avoids the danger of the device being thrown out of adjustment. y

Each arm is preferably provided with a plurality of small slots of perforations such as 15 throughout its entire working length so as to afiord a maximum exposure and uniformity of action. Each arm is also preferably slotted as at 16 along its center line at its wider or base portion so as to minimize cross sectional warping and the consequent reduction of effective contact movement.

The parts are so arranged, constructed and adjusted that the tips 17 and 18 of the thermostatic arms upon change in temperature travel in the direction of the dotted lines as shown in Fig.- 6 so that one tip scrapes across the other. This insures electrical contact eventhough one or both of the contacts becomes coated with dirt or other non-conductive material.

As before. intimated the shape of the circult terminals 3 and 4 and other features of construction not herein claimed are immaterial. In Figs. 5, 6 and 7 another modification of the support of the thermostatic arms is shown. In this case a bolt 20 and a nut 21 may be considered as the equivalent of the screw 10 for adjusting the support 22. The arm 2 is supported directly by a flange 23 of the plate 4:.

lit will be obvious to those acquainted with this art that changes may be made in details of construction without departing from the spirit and scope of my invention and that the arms can be arranged so as to make contact either upon a decrease or increase of temperature. The terms of the claims are therefore used in a descriptive sense rather than as terms of limitations except so far as required by the state of the 'prior art.

Jfree ends of the arms closely adjacent and arranged to move toward each other on intersecting paths in the expansive action of said arms, the said free ends of the arms having contact tips and the contact tip carried by the free, end of one of the said arms being inclined with respect to the path 0t travel of the contact tip of the other arm, whereby to produce in the expansive movement of the thermostatic arms a sliding, wiping contact of one contact tip in engagement with the other.

2. In a thermostat, two expansible thermostatic arms, means supporting" said arms with their free ends closely adjacent each other and movable toward each other on intersecting angles and guard devices for the free ends of said arms whereby to prevent accidental displacement of the free ends of said arms with respect to each other.

3. In a thermostat, a contact and a thermostaticarm supported at one end and free a to expand longitudinally at its opposite end into engagement with the said contact, the said thermostatic arm being centrally slotted longitudinally throughout the working length thereof to divide the working length into two transversely separated parts and thereby preventtransversely continuous L wardly under influence of heat and the other arranged to expand inwardly under influence of heat and means supporting said curved arms with their free ends closely approaching each other with the free end of the outwardly expanding arm disposed in- 13 longitudinal disengagement of the arm from said'slot.

6. In a thermostat, a support for a thermostatic arm, comprising an anchoring yoke having parallel side portions spaced apart and provided with oppositely alined slots to receive the base end of a thermostatic arm, and a thermostatic arm having its end engaged in the alined slots in the parallel side portions of the yoke.

7. In a thermostat, a supporting member having a main portion and spaced outstanding anchoring portions extending laterally therefrom, a thermostatic member carried by the outstanding anchoring portions of the said supporting member and spaced apart from the main portion thereof, one of the said members being slotted and the other member fitting therein and means securing the one member in its slotted engagement in the other member.

HENRY E. REEVE.

Witnesses:

ROBT. S. ALLYN, E. BRADFORD. 

